1. Field of the Invention
The present invention relates to multi-dimensional computer networks. More particularly, the present invention relates to a switched node comprising a disk controller with integrated multi-port switching circuitry.
2. Description of the Prior Art
A switched fabric is a multi-dimensional computer network wherein each node in the network comprises multiple ports for routing data in multiple dimensions (e.g., x and y). The bandwidth of switched fabric networks increases as new nodes are added which is a significant advantage over conventional single-dimensional networks. Rather than arbitrate for a single communication medium, data is routed in multiple dimensions which alleviates arbitration and blocking within the network.
Storage for switched fabric networks has in the past been implemented by attaching a storage subsystem to the edge of the fabric. One example illustrated in FIG. 1 is a fibre channel arbitrated loop (FCAL) which comprises a number of disk drives 20-2N communicating over a shared transmission medium 4 which attaches to the edge of the switched fabric network 8 through appropriate adapter circuitry 6. Host initiators 9A and 9B send storage access requests through the switched fabric network 8, which are serviced via the adapter circuitry 6. This implementation provides limited performance since the access requests must be serviced one at a time due to the single-dimensionality of the shared communication medium 4 (i.e., the arbitrated loop).
The project xe2x80x9cISTORExe2x80x9d at the University of California, Berkeley proposes to attach a disk drive at the periphery nodes of a conventional crossbar switch to achieve a non-blocking, parallel access network storage system. However, the ISTORE project proposes to attach a conventional disk drive at each periphery node of the crossbar switch through multi-port switching circuitry implemented external to the disk drive. This requires adapter circuitry within the switching circuitry for converting network formatted data (typically network packets) into a format compatible with the interface protocol for the disk drive (e.g., the ATA protocol). That is, the adapter circuitry must first convert the network-formatted data into logical block addresses compatible with the disk drive interface protocol. A disk controller within the disk drive then converts the logical block addresses into physical block addresses which correspond to physical storage locations (typically sectors) on the disk. This increases the expense and access latency of the network storage system due to the adapter circuitry in each periphery node of the crossbar switch. Further, the ISTORE architecture suggests a predetermined, static topology for the network as determined by the crossbar switch implemented external to the disk drive.
There is, therefore, a need to reduce the cost and access latency of a network storage system. Further, there is a need to dynamically configure a network into a selected topology, as well as for the network to self-discover its topology once configured.
The present invention may be regarded as a switched node for use in a switched fabric network. The switched node comprises a disk and a head actuated over the disk. An integrated disk controller within the switched node comprises more than two bi-directional ports for simultaneously transmitting data in multiple directions through the switched fabric network, each port comprising an input port and an output port. The disk controller further comprises interface circuitry for interfacing with the head, a data buffer for storing data received from the input ports and data received from the head via the interface circuitry, and routing circuitry responsive to header data received from the input ports and header data received from the interface circuitry.
In one embodiment, the interface circuitry processes data received from the data buffer in order to store the data on the disk without mapping logical block addresses into physical block addresses. This avoids the overhead and cost of the prior art adapter circuitry which converts network data into a conventional disk drive interface protocol.
In another embodiment, the bi-directional ports in the switched node are dynamically configurable to connect to bi-directional ports of other switched nodes. And in yet another embodiment, the switched node comprises a self-discovery facility for use in discovering the topology of the switched fabric network.
The present invention may also be regarded as a switched fabric network comprising a plurality of interconnected switched nodes. Each switched node comprises a disk and a head actuated over the disk. An integrated disk controller within each switched node comprises more than two bi-directional ports for simultaneously transmitting data in multiple directions through the switched fabric network, each port comprising an input port and an output port. Each switched node further comprises interface circuitry for interfacing with the head, a data buffer for storing data received from the input ports and data received from the head via the interface circuitry, and routing circuitry responsive to header data received from the input ports and header data received from the interface circuitry.